The present invention relates to a reflector antenna suitable for use in transmit and/or receive mode, and in particular suitable for use on board geostationary communications satellites.
Such satellites have large deployable reflectors of dimensions that commonly reach 10 meters (m) to 15 m. They are powered by feeder arrays of large dimensions. In order to approximate to a parabolic profile, the reflectors are organized in a meshed array which is put into place and held under tension by a complex system that implements cables. One such parabolic and deployable reflector is described in U.S. Pat. No. 4,811,034 (TRW).
As an indication, a reflector having a diameter of 12 m using that technology weighs about 100 kilograms (kg) and costs about 10,000,000 Euros.
An object of the present invention is to provide a reflector antenna suitable for approximating a reference surface such as a parabolic surface from a much smaller number of panels.
The idea on which the invention is based is to provide electronic correction, at least in part, for the approximation to the reference surface that is due to implementing multiple panels.
The invention thus provides a reflector antenna characterized in that it comprises a plurality of panels assembled edge to edge to form a non-plane surface constituting an approximation to a reference surface, and a beam-forming device generating a beam-forming function for an array of antenna elements coupled to said panels, and in that said beam-forming function presents at least one surface error correction term for compensating at least in part the difference between the surface constituted by the assembled panels, in particular plane panels, and said reference surface, in particular a parabola, and/or in that at least some of said panels have reflector elements provided with fixed or variable compensation means for compensating said difference, at least in part.
The panels can be made of carbon fiber or they can be constituted by a mechanically tensioned wire mesh or indeed mesh under mechanical tension that is covered in metal. They can also be constituted by membranes.
In a variant, the panels can be reflecting arrays, each constituted by an array of such reflecting elements.
At least some of said reflecting elements can be coupled to phase shifters that give rise to fixed delays and/or to phase shifters giving rise to variable delays, and constituting said compensation means.
At least some of the reflecting elements can present two elements that are polarized perpendicularly relative to each other and interconnected by a transmission line that gives rise to a fixed delay.
At least some of the reflector elements can present two elements that are polarized perpendicularly relative to each other and that are interconnected by a phase shifter giving rise to a variable delay.
The panels can be plane and rigid. In a variant, the panels which are, for example, plane, can be flexible and subjected to mechanical tension, e.g. by means of a cable, so as to give them a shape that is not plane.
Beam formation can be implemented in baseband or at intermediate frequency. The beam-forming device can be analog, digital, or of combined analog-and-digital technology.